-- Add warranty mileage (KM) field to bids table
-- Suppliers can specify warranty in either months OR kilometers

ALTER TABLE `bids` 
ADD COLUMN `warrantyMileage` INT NULL COMMENT 'Warranty period in kilometers (if warrantyAvailable is true)' AFTER `warrantyPeriod`;

-- Note: At least one of warrantyPeriod (months) or warrantyMileage (KM) should be filled
-- if warrantyAvailable is true. This will be enforced in the application layer.